The cost- effectiveness of early dental visit in infants and toddlers focused on regional deprivation in South Korea: A retrospective cohort study

Background The aims of this study are to evaluate the cost-effectiveness of early dental visits (EDVs) and to investigate how regional deprivation impacts the economic evaluation. Methods This study used the South Korea National Health Insurance database, which included medical claim data and voluntary-based oral examination data. The subjects of this study included whole participants for oral examinations for infants and toddlers of the National Health Insurance Corporation. A retrospective cohort study was designed and measured all oral treatments, costs, and number of visits for 208,969 children (experimental group, 101,768; non- experimental group, 107,201) who underwent oral examination for infants and toddlers from 2007 to 2014. The cost-effectiveness was measured using the incremental cost-effectiveness ratio, and the T-health index was used as the measurement for effectiveness. In addition, the difference in the effect according to the level of regional deprivation was confirmed. Results The findings of this study showed that EDVs were cost-effective and that children who participated in EDVs had better oral health (T-health-2 index difference 0.32 point in most deprived regions) and needed 5 USD less costly dental treatments than those who did not have EDVs. The cost-effectiveness of EDVs varied according to the level of regional deprivation and was the highest in the most deprived regions. Conclusions The study findings suggested that the provision of oral examination for infants and toddlers was a cost-effective dental policy. Additionally, EDVs were more effective in children who resided in the most deprived regions, a finding that will lead to the development of policy intervention to improve dental care despite spatial inequality for disadvantaged population groups. Regarding the distribution of dental hospitals/clinics, incentive based dental polices for either dental providers or patients are needed that will assure the delivery of dental care despite spatial inequality.

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• If neither of these applies but you are able to provide details of access We wish to submit a new manuscript titled, "The cost-effectiveness of early dental visit in infant and toddlers focused on regional deprivation in South Korea: A retrospective cohort study" for consideration by the PLOS ONE In this paper, we report on the cost-effectiveness of early dental visits, which was defined as dental utilization for oral examination during infant period, using incremental cost effectiveness ratio. The authors seek to explore the cost-effectiveness of early dental visits (EDVs) and to investigate how regional deprivation impacts the economic evaluation. Through this study, we confirmed that early dental visits (EDVs) are an appropriate policy to efficiently use scarce medical resources from an individual as well as social point of view.
Thank you for your consideration of this manuscript. ratio, and the T-health index was used as the measurement for effectiveness. In addition, the 35 difference in the effect according to the level of regional deprivation was confirmed.

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Results : The findings of this study showed that EDVs were cost-effective and that children 37 who participated in EDVs had better oral health (T-health-2 index difference 0.32 point in most 38 deprived regions) and needed 5 USD less costly dental treatments than those who did not have 39 EDVs. The cost-effectiveness of EDVs varied according to the level of regional deprivation 40 and was the highest in the most deprived regions. to prevent and eliminate future dental caries and thus reduce dental-related costs.

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The guidelines for the prevention of ECC include the following: self-care, use of 67 professional services, and exposure to community interventions such as water fluoridation[4,9-68 11]. One of the prevention recommendations was the early dental visit (EDV), which was 69 reported to reduce both dental caries and the burden of dental-related costs [5,12], . The EDV 70 was reported to be associated with fewer dental visits for children [5,11]. Other studies found a 71 relationship between the EDV and dental costs or treatment use [13,14]. These studies 72 emphasized that early prevention translated into a significant cost savings for dental care, 73 especially for families at or below the poverty level.  . We operationally defined the EDV 118 (exposed group) as the first dental visit in which dental services were utilized for oral 119 examination prior to 24 months of age. In the non-EDV (non-exposed group), toddlers who did 120 not undergo oral examination at 24 month were classified. A total of 208,969 were included as 121 subjects. At this time, 101,768 people in the experimental group and 107,201 people in the 122 non-experimental group were included, respectively. The study compared the cost-123 effectiveness between the 'exposed (EDV)' group and the 'non-exposed (non-EDV)' group.  The dmft index was defined as a decayed teeth have untreated legion, filled teeth have 178 been repaired with restorative treatment, and missing teeth have been extracted caused by 179 dental caries. It was included for comparison with T-Health index.

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In this study, effectiveness was measured using the incremental cost-effectiveness ratio,  Considered variables 190 We used gender, income, and regional variable for analysis. The income level was derived from the health insurance premium of the National Health Insurance program, because NHI is 192 mandated for all citizens, and the premium is imposed on the basis of income or assets of the 193 insured. A variable considered to the regional variable was the composite deprivation index  Table 1 shows the general characteristics of the subjects. The overall EDV rate was 48.70%

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(101,768) and was higher in the affluent group. As the income level increased, the EDV rate 205 tended to increase. The differences in the rates of EDV between most poor and most affluent 206 income levels were large in the regions with a high CDI score, which is most deprived areas.

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The number of dental visits was higher in the EDV group and increased as the CDI score 208 decreased. In contrast, the cost of dental services was inversely related to the number of visits.

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The cost of dental services was higher in the non-EDV group than in the EDV group (Table 1). The effectiveness of early dental visits 218 When comparing the T-Health index scores, the T-Health index scores of the EDV group 219 were higher than those of its counterpart. The lowest scores occurred in the "middle CDI" 220 regions, followed by the "low CDI" regions and the "high CDI" regions. Considering T-Health-221 2 as an example, the difference between the two groups (EDV vs. Non-EDV) in the "low" CDI 222 regions was 0.25; the difference in the "middle" regions was 0.21; and the difference in the 223 "high" regions was 0.32. However, the dmft index increased as the CDI score increased. The 224 difference between the EDV group and the non-EDV group could be confirmed according to 225 the type of T-health index whose measurement value was changed depending on whether or 226 not dental treatment was received. However, the difference in the dmft index between the EDV 227 and non-EDV groups was not consistent (  The cost-effectiveness of early dental visits 235 The ECC prevention effects of the EDV according to the regional deprivation index are  Municipality socio-economic status could influence the oral health and accessibility of 254 dental services, we also investigated how regional deprivation impacted incremental cost-255 effectiveness of EDVs. The results of this study showed that EDVs were cost-effective and that 256 the effectiveness was the highest in the high CDI regions. In other words, these results mean 257 that there is a cost-effectiveness in areas where there is a slope in the dental accessibility, and 258 it suggests that the provision of such preventive services can contribute to oral health equity[5].

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In this study, comparing the average number of dental visits per child between the non-260 EDV group and the EDV group, as shown in Table 1, it was found that the average number of 261 dental visits in the EDV group was higher than that of the non-EDV group. However, when 262 comparing the total cost of dental service, it was confirmed that the results were contradictory.

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The difference in total cost of dental service between the two groups tended to increase in areas 264 where regional deprivation was severe, which was a result of supporting the previous 265 researches[10,12].

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The T-Health index was used instead of the dmft index to show the effectiveness of the the T-Health index helped to conclude that better oral health was maintained through early 280 dental visits.

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In this study, we found that the EDV group incurred less dental costs than the non-EDV 282 group. In spite of the fact that the number of dental visits for children who experienced EDVs 283 was higher than for children who did not participate in EDVs, the average cost per dental visit 284 showed that children who experienced EDVs spent less. It was thought as a result of the timely 285 intervention of dental services, which reduce the overall costs associated with dental treatments, 286 and that untreated dental diseases became more severe and costly because treatments were is of the significance in that it suggested the necessity of a regional approach to the distribution 313 of dental care by measuring the cost-effectiveness of EDV according to the level of regional All relevant data are within the paper and its Supporting Information files. (EDVs) and to investigate how regional deprivation impacts the economic evaluation. EDVs. The cost-effectiveness of EDVs varied according to the level of regional deprivation 40 and was the highest in the most deprived regions. to prevent and eliminate future dental caries and thus reduce dental-related costs.

66
The guidelines for the prevention of ECC include the following: self-care, use of 67 professional services, and exposure to community interventions such as water fluoridation[4,9-68 11]. One of the prevention recommendations was the early dental visit (EDV), which was 69 reported to reduce both dental caries and the burden of dental-related costs [5,12], . The EDV 70 was reported to be associated with fewer dental visits for children [5,11]. Other studies found a 71 relationship between the EDV and dental costs or treatment use [13,14]. These studies 72 emphasized that early prevention translated into a significant cost savings for dental care, . We operationally defined the EDV 119 (exposed group) as the first dental visit in which dental services were utilized for oral 120 examination prior to 24 months of age. In the non-EDV (non-exposed group), toddlers who did effectiveness between the 'exposed (EDV)' group and the 'non-exposed (non-EDV)' group. 3) Cost-effectiveness 178 The dmft index was defined as a decayed teeth have untreated legion, filled teeth have 179 been repaired with restorative treatment, and missing teeth have been extracted caused by 180 dental caries. It was included for comparison with T-Health index.

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In this study, effectiveness was measured using the incremental cost-effectiveness ratio,

Considered variables
We used gender, income, and regional variable for analysis.  Table 1 shows the general characteristics of the subjects. The overall EDV rate was 48.70%

207
(101,768) and was higher in the affluent group. As the income level increased, the EDV rate 208 tended to increase. The differences in the rates of EDV between most poor and most affluent 209 income levels were large in the regions with a high CDI score, which is most deprived areas.

210
The number of dental visits was higher in the EDV group and increased as the CDI score 211 decreased. In contrast, the cost of dental services was inversely related to the number of visits.

212
The cost of dental services was higher in the non-EDV group than in the EDV group (Table 1).  were higher than those of its counterpart. The lowest scores occurred in the "middle CDI" 223 regions, followed by the "low CDI" regions and the "high CDI" regions. Considering T-Health-224 2 as an example, the difference between the two groups (EDV vs. Non-EDV) in the "low" CDI 225 regions was 0.25; the difference in the "middle" regions was 0.21; and the difference in the 226 "high" regions was 0.32. However, the dmft index increased as the CDI score increased. The 227 difference between the EDV group and the non-EDV group could be confirmed according to 228 the type of T-health index whose measurement value was changed depending on whether or 229 not dental treatment was received. However, the difference in the dmft index between the EDV The cost-effectiveness of early dental visits 238 The ECC prevention effects of the EDV according to the regional deprivation index are Municipality socio-economic status could influence the oral health and accessibility of 260 dental services, we also investigated how regional deprivation impacted incremental cost-261 effectiveness of EDVs. The results of this study showed that EDVs were cost-effective and that 262 the effectiveness was the highest in the high CDI regions. In other words, these results mean 263 that there is a cost-effectiveness in areas where there is a slope in the dental accessibility, and 264 it suggests that the provision of such preventive services can contribute to oral health equity [5].

265
In this study, comparing the average number of dental visits per child between the non-

266
EDV group and the EDV group, as shown in Table 1, it was found that the average number of 267 dental visits in the EDV group was higher than that of the non-EDV group. However, when 268 comparing the total cost of dental service, it was confirmed that the results were contradictory.

269
The difference in total cost of dental service between the two groups tended to increase in areas 270 where regional deprivation was severe, which was a result of supporting the previous 271 researches[10,12].

272
The T-Health index was used instead of the dmft index to show the effectiveness of the higher T-health index score indicates a healthier oral status, and using the T-Health index 287 helped to conclude that better oral health was maintained through early dental visits.

288
In this study, we found that the EDV group incurred less dental costs than the non-EDV 289 group. In spite of the fact that the number of dental visits for children who experienced EDVs 290 was higher than for children who did not participate in EDVs, the average cost per dental visit 291 showed that children who experienced EDVs spent less. It was thought as a result of the timely 292 intervention of dental services, which reduce the overall costs associated with dental treatments, 293 and that untreated dental diseases became more severe and costly because treatments were In conclusion, in terms of early intervention in the life course through early dental visits, 317 providing oral examinations for infants and toddlers was a cost-effective policy. Additionally,

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EDVs were more effective in individuals who resided in the most deprived regions. This study 319 is of the significance in that it suggested the necessity of a regional approach to the distribution 320 of dental care by measuring the cost-effectiveness of EDV according to the level of regional Additional Editor Comments (if provided): The authors appreciated your critical review comments. And we are very honored to give you the opportunity to submit your revised manuscript.
Line 52: US data reported is quiter old. Can it be updated?
-Yes, we have updated it to reflect your comments.
line 83: PLease the sentence construction. Seems like some missing information.
-We modified it to reflect your comments.
Lines 136 and 145 are repeated…. can be avoided -Line 136 is the description of the variables used in the previous study, and line 145 is the definition of the operant variable in this study. We are very sorry that we did not make any special modifications to this.
Tsble 1 -check quintiles -Yes, We checked it DMFT index values have not been explained in the methods, so not clear why it is contradictory to expectations in Line 269.
-First of all, thanks for your comments. However, in the introduction and research method, the study using DMFT was explained earlier, and the discussion was to explain the difference between this study and other studies. However, as you commented, some parts of the sentences were not clearly expressed, so we have corrected them.
please read thoroughly to correct the grammar. Several sentences do not read well.
-We modified it to reflect your comments.

Comment: Anil Gumber
Paper is well written but lack methodological rigour. It is not clear to me in what perspective health economic evaluation is done. Author mentioned social perspective, but in paper it does not reflect in terms of loss of productivity of parents who care for their children in lieu of using dental services. The ICER is not presented well. I can't make out any thing from graphs representing negative ICER bars. The paper clearly lack focus in terms of analysis, costs and benefits. The authors need to present cost-effectiveness overall and then look by level of deprivation. The deprivation cut-off levels are arbitrary and to nullify it it should be use tertile or quartie or quintile break-up.
The authors appreciated your critical review comments. And we are very honored to give you the opportunity to submit your revised manuscript. In response to your comments, we have revised the manuscript as follows.
1. Author mentioned social perspective, but in paper it does not reflect in terms of loss of productivity of parents who care for their children in lieu of using dental services.
-The social point of view considered by the authors was the difference in the effect depending on the degree of deprivation in the region. Accordingly, the text has been modified as follows to convey a clearer meaning.
Therefore, this study was conducted with the aim of confirming the effectiveness of the OEIT through the economic evaluation. In particular, it was attempted to determine the difference according to regional deprivation. …… …..; and (2) To find if the costeffectiveness differs according to the level of community deprivation and to determine if the most deprived areas are associated with greater effectiveness .
-As you commented, it would have been better if the cost of lost productivity due to childc Response to Reviewers are had been taken into account. Unfortunately, the authors were unable to fully account f or all variables in this study using secondary data. In this regard, we have added your co mments to the research methods and limitations of the research .
As previously stated, we will conduct further research in the future, taking into account y our comments. However, we ask for your understanding of some of the shortcomings of this study.
In consideration of your opinion, the text has been written as follows :

Methods
This study did not take into account the cost of loss of productivity and travel cost, so the cost-effectiveness of EDV and non-EDV compared by calculating the direct medical cost covered by insurance for five years after the infant oral examination, excluding the indire ct cost.

Discussion
However, due to the limitation of the secondary data, there is a limitation in that indirect costs (travel cost, care cost etc), were not considered when calculating cost-effectiveness.
Accordingly, in continued research, efforts to include appropriate variables that can suffi ciently consider cost-effectiveness should be continued.
2. The ICER is not presented well. I can't make out any thing from graphs representing nega tive ICER bars.
-Thank you for your critical comments. We have made the following changes to reflect your comments.
At this time, negative ICER values that are shown in Figure 3 were due to positive effectiveness of natural units on teeth and the occurrence of treatment costs according to the condition of the teeth, which means a reduced cost between the non-EDV and EDV groups (Figure 3).
3. The deprivation cut-off levels are arbitrary and to nullify it it should be use tertile or quartie or quintile break-up.
-Thank you for your critical comments following a detailed review. Even though our authors have already classified using the tertile, it seems that they did not describe the content sufficiently. We have made the following changes to reflect your comments.
The CDI score was categorized into 3 groups using tertile as follows: low, middle, and hi gh, with the low group being considered more affluent.